Electrical automotive side-channel fluid pump

The invention is directed to an electrical automotive side-channel fluid pump for pumping a liquid or a gaseous medium in particular within a circuit of an auxiliary unit of a vehicle.

Side-channel pumps are, in some aspects, similar to centrifugal pumps which need to have a dynamic sealing, or, if they are electrically driven, can be provided with a canned electric motor for fluidically isolating the motor stator and the motor electronics from the fluid. The canned electric motor comprises a motor rotor and a motor stator which are fluidically separated by a thin-walled separating can being arranged within the air gap between the motor rotor and the motor stator. Such a design requires an electronic commutation of the canned electric motor which, in turn, requires power electronic components for driving the electric motor.

The canned electric motor allows to flood the motor rotor chamber with the pumped fluid for cooling the electric motor as well as for cooling the power electronic components. An appropriate flow control of the fluid through the pump housing along the heat-loaded components using a branched-off partial flow of the pumped total volume flow provides a pump internal self-supplied cooling circuit which prevents the pump from overheating. Typically, the partial volume flow as a cooling flow is branched off at the discharge zone of the pump and is returned to the suction zone of the pump to provide a relatively large pressure gradient which induces the cooling flow to flow properly. The application of this cooling circuit being fed with fluid from the pumping chamber results in a reduction of the total discharged flow rate of the pump and, accordingly, reduces the pump efficiency.

It is an object of the invention to provide a simple and relatively cost efficient electrical automotive side-channel fluid pump which provides a constant and reliable cooling flow for cooling the electric motor and/or the power electronic components without significantly reducing the total pump efficiency.

This object is achieved with an electrical automotive side-channel fluid pump according to the invention with the features of main claim 1.

An electrical automotive side-channel fluid pump according to the present invention comprises a static pump housing with a pumping section and a motor section. The pumping section is substantially defined by a ring-type side-channel being provided with a side-channel suction zone and a side- channel discharge zone. A pump rotor is rotating within the pumping section, the pump rotor being provided with a plurality of rotor blades which are moved through the side-channel, so that a flow direction is defined. The side-channel comprises a pumping side-channel segment which extends, seen in flow direction, from the side-channel suction zone to the side-channel discharge zone. Within the pumping side-channel segment, the fluid which is flowing into the side-channel through an inlet duct within the suction zone is pumped through the pumping side-channel segment by the rotor blades. The rotor blades displace the fluid which, as a result, performs a vortex-like flow within each pumping compartment being defined by two adjacent rotor blades and within the blade-free section of the pumping side-channel segment. Thereby, the pressure of the pumped fluid is increased continuously towards the discharge zone. Within the discharge zone, the pumped fluid is then discharged through an outlet duct.

Compared to a conventional centrifugal pump, a side-channel pump does not completely discharge the pumped fluid within the discharge zone. After the discharging process, a relatively small volume of the pumped fluid which has been pumped through the pumping side-channel segment remains within each pumping compartment. This non-discharged fluid is transported back to the suction side through a non-pumping side-channel segment which extends, seen in rotational direction, from the discharge zone to the suction zone.

The pump rotor is electrically driven by an electric motor which is arranged within the motor section of the pump housing. This motor section is arranged adjacent to the pumping section. For driving the electric motor, several power electronic components are arranged preferably within a hermetically sealed motor section dry zone which is fluidically separated from a wet zone within the motor section by a separating can. This wet zone is in particular that zone which is flooded with the pumped liquid or gaseous fluid. The separating can can be provided with an integral separating bottom wall or a separating tube with a separate bottom wall. A cooling circuit is provided to define a pumped fluid cooling flow through or around the motor section, for cooling the electric motor and the power electronic components.

The pumped fluid cooling flow is branched off of the side-channel via a cooling circuit inlet opening and is guided into the motor section, preferably into the wet zone of the motor section in which the motor rotor is preferably arranged, i.e., the motor rotor and a motor stator of the electric motor are preferably fluidically separated from each other by the separating can, wherein the motor stator is preferably arranged within the dry zone of the motor section. The cooling flow is then guided through the motor section such that a constant cooling flow is provided which dissipates the heat generated by the electric motor and/or the power electronic components. After the cooling flow has absorbed the heat, it is returned to the side- channel via a cooling circuit outlet opening.

At least the cooling circuit inlet opening or the cooling circuit outlet opening is arranged within the non-pumping side-channel segment. In contrast to the pumping side-channel segment with its blade-free side-channel- section, the non-pumping side-channel segment has no blade-free side- channel-section which fluidically connects the pumping compartments, respectively. As a result, the non-discharged fluid remains within each pumping compartment entering the non-pumping side-channel segment after the discharging process and is carried through the non-pumping side- channel segment towards the suction zone. Thereby, the pressure within every pumping compartment is reduced. If, for example, the cooling circuit inlet opening is arranged within the non-pumping side-channel segment, the non-discharged fluid can be used for supplying the cooling circuit. According to the invention, the non-discharged fluid can be used to supply the cooling circuit. As a result, the cooling flow is not branched off of the total discharged volume flow, so that the flow rate of the total discharged volume flow is not relevantly affected and, accordingly, the pump efficiency is not relevantly reduced by the application of the cooling circuit.

After the cooling flow has flown through the motor section, the cooling flow can be returned, for example, into the suction zone, where it mixes up with cool fluid being sucked into the side-channel through the inlet duct. Depending on the positioning of the cooling circuit inlet opening within the non-pumping side-channel segment, a sufficient pressure gradient between the cooling circuit inlet opening and the cooling circuit outlet opening can be provided, resulting in a constant or continuous and in a sufficient cooling flow through the motor section.

In a preferred embodiment of the invention, both the cooling circuit inlet opening and the cooling circuit outlet opening are arranged within the non- pumping side-channel segment. The cooling flow is not only branched off from the non-pumping side-channel segment, but is also returned to the non-pumping side-channel segment. The cooling circuit inlet opening is preferably arranged upstream of the cooling circuit outlet opening to ensure a sufficient pressure gradient between the cooling circuit inlet opening and the cooling circuit outlet opening so that a constant or continuous cooling flow flows through the motor section.

Preferably, the circumferential distance between the cooling circuit inlet opening and the cooling circuit outlet opening is larger than the circumferential distance between two adjacent rotor blades. Thereby, a shortcut between the cooling circuit inlet opening and the cooling circuit outlet opening is avoided, because the openings are never fluidically connected to each other via a pumping compartment.

In a preferred embodiment, the cooling circuit inlet opening and/or the cooling circuit outlet opening is arranged at that axial side of the side- channel which faces the motor section. As a result, a relatively short and direct fluidic connection is provided between the pumping section and the motor section resulting in a relatively short flow length. For example, a straight and easy manufacturable borehole could be used to fluidically connect the pumping section and the motor section.

In a preferred embodiment of the invention, the circumferential distance between at least one of the cooling circuit openings which is arranged within the non-pumping side-channel segment and the pumping side- channel segment is larger than the circumferential distance between two adjacent rotor blades. The circumferential distance in particular refers to that point, where the following rotor blade of two adjacent rotor blades has completely arrived at the non-pumping side-channel segment so that at least one pumping compartment being neither connected to the pumping side-channel segment nor to one of the cooling circuit openings fluid ically separates the pumping side-channel segment from the cooling circuit inlet opening or from the cooling circuit outlet opening. Thereby, a fluidic shortcut between the cooling circuit and the pump fluid flowing in the pumping side-channel segment is avoided.

Preferably, the cooling circuit comprises a cooling circuit inlet channel and a cooling circuit outlet channel for fluidically connecting the side-channel with the wet zone. The cooling circuit inlet channel can be fluidically connected via the cooling circuit inlet opening to the non-pumping side- channel segment or to the pumping side-channel segment which also comprises the discharge zone with the outlet duct. Accordingly, the cooling circuit outlet channel can be fluidically connected via the cooling circuit outlet opening to the non-pumping side-channel segment or to the pumping side-channel segment which also comprises the suction zone with the inlet duct.

In a preferred embodiment of the invention, the cooling circuit inlet opening and/or the cooling circuit outlet opening are/is arranged within the radius of the rotor blades, i.e., both cooling circuit openings are located, seen in a radial direction between the minimum rotor blade radius and the maximum rotor blade radius. Thereby, the cooling circuit openings are within the direct effective range of the rotor blades resulting in a sufficient inflow and outflow of the fluid into and out of the cooling circuit. In a preferred embodiment of the invention, the electrical automotive side- channel fluid pump comprises a hollow drive shaft with a connection channel extending axially through the hollow drive shaft. The hollow drive shaft mechanically connects the electric motor with the pump rotor. The connection channel is preferably used for guiding the cooling flow from one axial end of the motor section to the other opposite axial end of the motor section. Accordingly, the connection channel is part of the cooling circuit. For example, if the cooling flow enters the motor section at that axial end being adjacent to the pumping section, the cooling flow flows through the motor section to the other opposite axial end and thereby absorbs the heat on its way through the motor section. At that other axial end, the cooling flow enters the connection channel of the hollow drive shaft and axially flows towards the pumping section back into the side-channel.

Alternatively, the cooling flow can flow in opposite direction, wherein the cooling flow flows from the side-channel through the connection channel of the hollow drive shaft so that the cooling flow enters the motor section at that axial end being opposite to the pumping section. The cooling flow then flows towards the pumping section through the motor section or preferably through the wet zone which is therefore a part of the cooling circuit and from there back into the side-channel.

Preferably, the power electronic components are in a heat transferring contact with the separating can. Usually, the power electronic components are arranged at a printed circuit board which is preferably arranged in a heat transferring contact with the separating can bottom wall which fluidically separates the wet zone and the dry zone of the motor section. The cooling flow flows along the separating can bottom wall within the wet zone and absorbs the heat being generated by the power electronic components and being transferred via the printed circuit board to the separating bottom wall. As a result, the heat is effectively dissipated to fluid and is then transported back to the pumping section.

Three embodiments of the invention are described with reference to the enclosed drawings, wherein figure 1 shows a schematic longitudinal cross-sectional view of a first embodiment of an electrical automotive side-channel fluid pump according to the invention wherein the cooling circuit inlet opening is arranged within the non-pumping side-channel segment and the cooling circuit outlet opening is arranged within the suction zone, figure 2 shows the electrical automotive side-channel fluid pump of figure 1 in a transversal cross-sectional view through the side-channel, figure 3 shows a schematic transversal cross-sectional view of a second alternative embodiment of an electrical automotive side-channel fluid pump according to the invention wherein both the cooling circuit inlet opening and the cooling circuit outlet opening are arranged within the non- pumping side-channel segment, and figure 4 shows a schematic transversal cross-sectional view of a third alternative embodiment of an electrical automotive side-channel fluid pump according to the invention wherein the cooling circuit inlet opening is arranged within the discharge zone and the cooling circuit outlet opening is arranged within the non-pumping side-channel segment.

Figure 1 shows an electrical automotive side-channel fluid pump 10 for providing pressurised oil to an automatic transmission of a vehicle. The electrical automotive side-channel fluid pump 10 comprises a substantially cylindrical static multipiece pump housing 12 comprising a pump cover 13, the pump housing 12 further comprising a motor section M and a pumping section P. The pumping section P is substantially defined by a ring-type side-channel 18 with a pumping side-channel segment 181 and a non- pumping side-channel segment 182. The pumping side-channel segment 181 extends, seen in flow direction F, from a suction zone S to a discharge zone D, shown in figures 2-4.

Furthermore, as shown in figure 1, an electric motor 30 is arranged within the motor section M, the electric motor 30 comprising a rotatable cylindrical motor rotor 31 and a static hollow-cylindrical motor stator 32 which circumferentially surrounds the motor rotor 31. The motor rotor 31 and the motor stator 32 are fluidically separated from each other by a separating can 17 with a hollow-cylindrical separating can sidewall 171 which is arranged within the air gap between the motor rotor 31 and the motor stator 32 and which radially encloses a wet zone WZ. The separating can 17 further comprises a flange-type separating can bottom wall 172 which axially encloses the wet zone WZ. Accordingly, the motor rotor 31 is arranged within the wet zone WZ being flooded with the pumped fluid, whereas the motor stator 32 is arranged within a dry zone DZ.

The motor rotor 31 is co-rotatably connected to a disc-type pump rotor 15 via a hollow-cylindrical drive shaft 25. The disc-type pump rotor 15 comprises a plurality of rotor blades 155 with a substantially rectangular cross-section. The rotor blades 155 extend radially outwards and are moved through the side-channel 18 by the rotational movement of the pump rotor 15. Thereby, the fluid, which is entering the side-channel 18 within the suction zone S through an axially oriented and hollow cylindrical inlet duct 14, is pumped through the pumping side-channel segment 181 towards the discharge zone D. The pump 10 comprises a cooling circuit 40, wherein the pumping section P and the motor section M are fluidically connected via a cooling circuit inlet channel 41 with a cooling circuit inlet opening 42 being arranged within the radius of the rotor blades 155 in the non-pumping side-channel segment 182 at that axial side of the side-channel 18 which faces the motor section M. Accordingly, the non-pumping side-channel segment 182 and the wet zone WZ are directly fluidically connected by a simple bore hole. The fluid being pumped through the side-channel 18 enters the wet zone WZ at a relatively high pressure level and defines a cooling flow which axially flows through the wet zone WZ towards the axial end being opposite to the pumping section P, where the cooling flow absorbs the heat generated by the electric motor 30. The cooling circuit 40 is therefore partially defined by the wet zone WZ.

The cooling fluid then flows radially inwards along the separating can bottom wall 172 and thereby absorbs the heat being generated by several power electronic components 50, in particular absorbs the heat of a centrically arranged power semiconductor 51, the power electronic components 50, 51 being arranged at a disk-shaped printed circuit board 55 which is arranged within the dry zone. The printed circuit board 55 is arranged adjacent to and in a heat transferring contact with the separating can bottom wall 172 so that the heat being generated by the power electronic components is transferred via the printed circuit board 55 and the separating can bottom wall 172 to the cooling flow.

At the separating can bottom wall 172, the heated cooling flow enters a connection channel 26 via a connection channel inlet opening 261, the connection channel 26 extending axially through the hollow drive shaft 25. The cooling flow then flows axially towards the pumping section P and flows out of the connection channel 26 through a connection channel outlet opening 262 into a transfer volume T being defined together by the pump rotor 25 and the pump cover 13. The transfer volume T is fluidically connected to the low-pressure inlet duct 14 via a cooling circuit outlet channel 44 so that the cooling flow flows through the cooling circuit outlet channel 44 and enters the inlet duct 14 through a cooling circuit outlet opening 45. As a result, the cooling flow is guided back to the suction zone S and mixes up with the cool fluid being sucked into the suction zone S via the inlet duct 14.

The figures 2-4 show three alternative embodiments of a side-channel 18 of an electrical automotive side-channel fluid pump 10, wherein figure 2 in particular shows the side-channel 18 of the electrical automotive side- channel fluid pump 10 of figure 1. The motor sections M of all three embodiments of the figures 2-4 are identically defined. The pumping side- channel segment 181 extends, seen in flow direction F, from the suction zone S to the discharge zone D. All three embodiments of the electrical automotive side-channel fluid pump 10 are provided with a tangentially oriented outlet duct 11. The embodiment of figure 2 and figure 4 are provided with an axially oriented inlet duct 14, as shown in figure 1, whereas the embodiment of figure 3 is provided with a tangentially oriented inlet duct 14.

The fluid is sucked into the side-channel 18 through the inlet duct 14 and enters the pumping side-channel segment 181 within the suction zone S. The rotor blades 155 move through the side-channel 18 in flow direction F so that the fluid is pumped through the pumping side-channel segment 181 from the suction zone S to the discharge zone D, where the fluid is discharged from the side-channel 18 and enters the circuit of an automatic transmission. Two adjacent rotor blades 155 define a pumping compartment 156, respectively, wherein each pumping compartment 156 moves the fluid through the side-channel 18. On its way from the suction zone S to the discharge zone D, the fluid is pressurised within the pumping side-channel segment 181 and is discharged via the outlet duct 11. Within the discharge zone , the fluid is not completely discharged, but a small volume of the fluid remains within each pumping compartment 156 and is carried into the non-pumping side- channel segment 182. In the embodiments of the figures 2 and 3, this non- discharged fluid supplies the cooling circuit 40 of the electrical automotive side-channel fluid pump 10.

The non-discharged fluid enters the cooling circuit 40 via the cooling circuit inlet opening 42 being arranged within the radius of the rotor blades 155 and flows through the cooling circuit 40 as described in the embodiment of figure 1. In contrast to the embodiment of figure 2, the cooling circuit outlet opening 45 of the embodiment of figure 3 is arranged in the non- pumping side-channel segment 182 within the radius of the rotor blades 155. The circumferential distance between the cooling circuit inlet opening 42 and the cooling circuit outlet opening 45 is larger than the circumferential distance between two adjacent rotor blades 155 so that a shortcut between the cooling circuit inlet opening 42 the cooling circuit outlet opening 45 is avoided.

In the embodiment of figure 3, the cooling circuit outlet channel 44 is defined by a machined groove 441 within the pump cover 13 which fluidically connects the transfer volume T with the non-pumping side- channel segment 182. The cooling flow which is flowing back through the connection channel 26 within the hollow drive shaft 25 flows via the transfer volume T and the groove 441 through the cooling circuit outlet opening 45 back into the non-pumping side-channel segment 182. In this embodiment the cooling circuit inlet opening 42 is arranged upstream of the cooling circuit outlet opening 45 so that a pressure gradient is provided between the high-pressure cooling circuit inlet opening 42 and the low- pressure cooling circuit outlet opening 45, the pressure gradient causing the cooling fluid to flow.

In the embodiment of figure 4, the cooling circuit inlet opening 42 is arranged within the pumping side-channel segment 181 within the discharge zone D. The cooling flow enters the cooling circuit 40 through the cooling circuit inlet opening 42 with in the pumping side-channel segment 181 and flows through the cooling circuit 40 as described in the embodiment of figure 1. As in the embodiment of figure 3, the cooling circuit outlet opening 45 is arranged within the radius of the rotor blades 155 in the non-pumping side-channel segment 182. As a result, the pressure gradient between the cooling circuit inlet opening 42 and the cooling circuit outlet opening 45 is higher than the pressure gradient of the embodiments of figure 2 and figure 3, but the cooling flow is branched off of the pump volume flow so that the total pumping efficiency is reduced compared to the embodiments of figure 2 and figure 3. In all three embodiments of the figures 2-4 the cooling circuit openings 42, 45 are arranged such that the circumferential distance between the cooling circuit openings 42, 45 and the pumping side-channel segment 181 of the side- channel 18 is larger than the circumferential distance between two adjacent rotor blades 155 having completely entered the non-pumping side-channel segment 182, i.e., if the, seen in flow direction F, following rotor blade 155 of two adjacent rotor blades 155 has not completely entered the non-pumping side-channel segment 182, the leading rotor blade 155 of the two adjacent rotor blades 155 must not have passed the cooling circuit opening 42, 45. Thereby, a shortcut between the cooling circuit openings 42, 45 being arranged within the non-pumping side- channel segment 182 and the pumping side-channel segment 181 is avoided.